The rise in urban population and increasing traffic congestion make metro systems a great way to navigate cities. However, expanding metro lines requires extensive underground development. These excavation projects frequently occur in close proximity to existing metro infrastructure, including stations and tunnels. Excavations are often conducted at zero distance on both sides of metro structures, which can significantly alter soil stress conditions, resulting in ground movement and structural deformation. Soft soil regions, such as the one in which Tianjin, China, is located, pose a particular risk, where excavation-induced heave can impact tunnel integrity and operational safety. Although there have been numerous studies on tunnel and station deformation due to adjacent excavation, most have focused on single-sided or isolated metro structures. The lack of research on asymmetrical bilateral zero-distance excavations leaves a critical gap in understanding the complex deformation behaviors and control strategies required for such scenarios.
A new paper, “Deformation and Control of Metro Structures during Asymmetric Bilateral Zero-Distance Excavations,” addresses this gap by investigating the deformation mechanisms of a metro station and tunnels in Tianjin subjected to asymmetrical bilateral zero-distance excavations. Researchers Jie Zhen, Gang Zheng, Junhua Huang, Senbin Lin, Hongbin Pei, Shen Gao, Qinghan Li, and Xuesong Cheng use field measurements and numerical simulations to analyze horizontal and vertical displacements, track torsion, and determine the effectiveness of various control measures. Their findings provide civil engineers with practical guidance for designing and managing underground construction projects that minimize risks to existing metro infrastructure. Learn more about how this research contributes to ensuring the safety, stability, and longevity of metro systems in the International Journal of Geomechanics at https://ascelibrary.org/doi/10.1061/IJGNAI.GMENG-10499. The abstract is below.
Abstract
With the continuous expansion of metro networks, zero-distance excavations on both sides of metro lines in urban underground spaces have become increasingly common. However, limited research has been conducted on the deformation response and corresponding control measures for such excavations. Based on extensive field measurements, this study analyzed the deformation of an existing metro station and tunnels caused by large-scale zero-distance asymmetric excavations on both sides. The results show that excavations caused massive heave of the metro station and tunnels, which exceeded the original control value by approximately 50% and 100%, respectively. The metro station transmitted the heave significantly, extending the influence range of the excavation to more than 10 times the excavation depth (H), which is much larger than the common 2H–4H excavation influence range; the tunnels exhibited lower transfer effects, and the influence range was 3H. The metro station had good structural integrity, exhibiting horizontal displacement toward the deeper excavation, while the twin tunnels moved in opposite horizontal directions and toward their respective adjacent excavation sides. The tracks inclined toward the excavation on the north side and away from the excavation on the south side, causing slight torsion along the longitudinal direction. Furthermore, measures to control metro station heave were examined, and the results indicated that surcharge loading was effective. The control effects of different loading schemes were further studied by numerical simulations. For the same total loading strength, compared to single-stage loading, multistage loading during excavation has better control effects when the heave is extremely large at greater excavation depth. The special influence characteristics of asymmetric bilateral excavations at zero distance on the metro structures and control methods discussed in this study can provide useful reference information and guidance in the future for more rapid development and utilization of underground space.
Learn more and get details on how to apply these findings to make your similar underground situation safer in the ASCE Library: https://ascelibrary.org/doi/10.1061/IJGNAI.GMENG-10499.
